Polymethylmethacrylate (PMMA) has been used in anterior and posterior stabilization of the spine for metastatic disease, as described by Sundaresan et al., "Treatment of neoplastic epidural cord compression by vertebral body resection and stabilization." J Neurosurg 1985;63:676-684; Harrington, "Anterior decompression and stabilization of the spine as a treatment for vertebral collapse and spinal cord compression from metastatic malignancy." Clinical Orthodpaedics and Related Research 1988;233:177-197; and Cybulski, "Methods of surgical stabilization for metastatic disease of the spine." Neurosurgery 1989;25:240-252.
Deramond et al., "Percutaneous vertebroplasty with methyl-methacrylate: technique, method, results [abstract]." Radiology 1990;117 (suppl):352; among others, have described the percutaneous injection of PMMA into vertebral compression fractures by the transpedicular or paravertebral approach under CT and/or fluoroscopic guidance. Percutaneous vertebroplasty is desirable from the standpoint that it is minimally invasive, compared to the alternative of surgically exposing the hard tissue site to be supplemented with PMMA or other filler.
The general procedure for performing percutaneous vertebroplasty involves the use of a standard 11 gauge Jamshidi needle. The needle includes an 11 gauge cannula with an internal stylet. The cannula and stylet are used in conjunction to pierce the cutaneous layers of a patient above the hard tissue to be supplemented, then to penetrate the hard cortical bone of the vertebra, and finally to traverse into the softer cancellous bone underlying the cortical bone.
A large force must be applied by the user, axially through the Jamshidi needle to drive the stylet through the cortical bone. Once penetration of the cortical bone is achieved, additional downward axial force, but at a reduced magnitude compared to that required to penetrate the cortical bone, is required to position the stylet/ tip of the cannula into the required position within the cancellous bone. If the force magnitude is not reduced appropriately, or if very soft bone is encountered, as is often the case with osteoporitic patients, the stylet and cannula can be accidentally and suddenly driven through the cortical bone on the opposite side of the vertebra. This is a very dangerous and potentially lethal situation in the case of vertebroplasty, since the aorta is located in close proximity to the anterior surface of at least the thoracic and lumbar vertebrae, and could easily be punctured by such an occurrence. Additionally, with regard to all vertebrae, the spinal cord is located medially of the pedicle, and could also be damaged by a piercing stylet.
Accordingly, there exists a need for a more controlled approach to the interior of a vertebral body for the performance of vertebroplasty and particularly, percutaneous vertebroplasty.